From ab8fed48419e0cf0d1c19a71fb1bf2c1063e42e3 Mon Sep 17 00:00:00 2001
From: Jane Tournois <jane.tournois@geometryfactory.com>
Date: Mon, 2 Jun 2025 11:22:38 +0200
Subject: [PATCH] use try/catch to pre-catch non-planar PLC facets when CDT_2
 fails

---
 .../CGAL/Conforming_constrained_Delaunay_triangulation_3.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h b/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
index 5bb76a99090..bcef1f3c6b8 100644
--- a/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
+++ b/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
@@ -1691,7 +1691,12 @@ private:
                       << tr().point(vh_2d->info().vertex_handle_3d)
                       << ")\n";
           }
-          cdt_2.insert_constraint(previous_2d, vh_2d);
+          try {
+            cdt_2.insert_constraint(previous_2d, vh_2d);
+          } catch(typename CDT_2::Intersection_of_constraints_exception&) {
+            // intersection of constraints probably due to the projection
+            CGAL_error_msg("Error : Input PLC facet is not coplanar!");
+          }
           previous_2d = vh_2d;
         }
       }